Mathematicians are like lovers. Grant a mathematician the least principle, and he will draw from it a consequence which you must also grant him, and from this consequence another.
A work of morality, politics, criticism will be more elegant, other things being equal, if it is shaped by the hand of geometry.
Leibniz never married; he had considered it at the age of fifty; but the person he had in mind asked for time to reflect. This gave Leibniz time to reflect, too, and so he never married.
Toute la philosophie n'est fondée sur deux choses: sur ce qu'on a l'esprit curieux et les yeux mauvais.
[Science originates from curiosity and bad eyesight.]
Nothing proves more clearly that the mind seeks truth, and nothing reflects more glory upon it, than the delight it takes, sometimes in spite of itself, in the driest and thorniest researches of algebra.
An educated mind is, as it were, composed of all the minds of preceding ages.
...as princes monopolize the earth, it is but fair that astronomers should have the sky for their share, and not suffer princes to intrude on their domain.
Nature is never so admired as when she is understood.